}
}
+ private static class FormatEntry {
+ final Format<?> format;
+ /** Number of times this format has been registered. */
+ final int refcnt;
+
+ public FormatEntry(Format<?> format, int refcnt) {
+ if (format == null)
+ throw new NullPointerException();
+ this.format = format;
+ this.refcnt = refcnt;
+ }
+ };
+
/**
* Available archival formats (corresponding to values for
* the --format= option)
*/
- private static final ConcurrentMap<String, Format<?>> formats =
- new ConcurrentHashMap<String, Format<?>>();
+ private static final ConcurrentMap<String, FormatEntry> formats =
+ new ConcurrentHashMap<String, FormatEntry>();
+
+ /**
+ * Replaces the entry for a key only if currently mapped to a given
+ * value.
+ *
+ * @param map a map
+ * @param key key with which the specified value is associated
+ * @param oldValue expected value for the key (null if should be absent).
+ * @param newValue value to be associated with the key (null to remove).
+ * @return true if the value was replaced
+ */
+ private static <K, V> boolean replace(ConcurrentMap<K, V> map,
+ K key, V oldValue, V newValue) {
+ if (oldValue == null && newValue == null) // Nothing to do.
+ return true;
+
+ if (oldValue == null)
+ return map.putIfAbsent(key, newValue) == null;
+ else if (newValue == null)
+ return map.remove(key, oldValue);
+ else
+ return map.replace(key, oldValue, newValue);
+ }
/**
* Adds support for an additional archival format. To avoid
* unnecessary dependencies, ArchiveCommand does not have support
* for any formats built in; use this function to add them.
- *
+ * <p>
* OSGi plugins providing formats should call this function at
* bundle activation time.
+ * <p>
+ * It is okay to register the same archive format with the same
+ * name multiple times, but don't forget to unregister it that
+ * same number of times, too.
+ * <p>
+ * Registering multiple formats with different names and the
+ * same or overlapping suffixes results in undefined behavior.
+ * TODO: check that suffixes don't overlap.
*
* @param name name of a format (e.g., "tar" or "zip").
* @param fmt archiver for that format
* @throws JGitInternalException
- * An archival format with that name was already registered.
+ * A different archival format with that name was
+ * already registered.
*/
public static void registerFormat(String name, Format<?> fmt) {
- // TODO(jrn): Check that suffixes don't overlap.
-
- if (formats.putIfAbsent(name, fmt) != null)
- throw new JGitInternalException(MessageFormat.format(
- JGitText.get().archiveFormatAlreadyRegistered,
- name));
+ if (fmt == null)
+ throw new NullPointerException();
+
+ FormatEntry old, entry;
+ do {
+ old = formats.get(name);
+ if (old == null) {
+ entry = new FormatEntry(fmt, 1);
+ continue;
+ }
+ if (!old.format.equals(fmt))
+ throw new JGitInternalException(MessageFormat.format(
+ JGitText.get().archiveFormatAlreadyRegistered,
+ name));
+ entry = new FormatEntry(old.format, old.refcnt + 1);
+ } while (!replace(formats, name, old, entry));
}
/**
- * Removes support for an archival format so its Format can be
- * garbage collected.
+ * Marks support for an archival format as no longer needed so its
+ * Format can be garbage collected if no one else is using it either.
+ * <p>
+ * In other words, this decrements the reference count for an
+ * archival format. If the reference count becomes zero, removes
+ * support for that format.
*
* @param name name of format (e.g., "tar" or "zip").
* @throws JGitInternalException
* No such archival format was registered.
*/
public static void unregisterFormat(String name) {
- if (formats.remove(name) == null)
- throw new JGitInternalException(MessageFormat.format(
- JGitText.get().archiveFormatAlreadyAbsent,
- name));
+ FormatEntry old, entry;
+ do {
+ old = formats.get(name);
+ if (old == null)
+ throw new JGitInternalException(MessageFormat.format(
+ JGitText.get().archiveFormatAlreadyAbsent,
+ name));
+ if (old.refcnt == 1) {
+ entry = null;
+ continue;
+ }
+ entry = new FormatEntry(old.format, old.refcnt - 1);
+ } while (!replace(formats, name, old, entry));
}
private static Format<?> formatBySuffix(String filenameSuffix)
throws UnsupportedFormatException {
if (filenameSuffix != null)
- for (Format<?> fmt : formats.values())
+ for (FormatEntry entry : formats.values()) {
+ Format<?> fmt = entry.format;
for (String sfx : fmt.suffixes())
if (filenameSuffix.endsWith(sfx))
return fmt;
+ }
return lookupFormat("tar"); //$NON-NLS-1$
}
private static Format<?> lookupFormat(String formatName) throws UnsupportedFormatException {
- Format<?> fmt = formats.get(formatName);
- if (fmt == null)
+ FormatEntry entry = formats.get(formatName);
+ if (entry == null)
throw new UnsupportedFormatException(formatName);
- return fmt;
+ return entry.format;
}
private OutputStream out;
projects / jgit.git / commitdiff